1. A term used by baby boomers as slang for making out, the term has more recently come to describe penetrating someones traecheotomy and/or other neck hole.
A: "Yeah and I blew a load right in her stoma."
2. The practice of greedily eating or drinking something, i.e. "getting it down your neck"
"LOL the slapper! How much beer DID she drink, then?"
"Must have had near fifteen. She was necking em like a sailor!!"